#include <iostream>
#include <vector>
using namespace std;
 
int main()
{
	int n = 0;
	cin >> n;
	vector<int> cost(n), dp(n + 1);
	for (int i = 0; i < n; ++i)
	{
		cin >> cost[i];
	}
	for (int i = 2; i <= n; ++i)
	{
		dp[i] = min(dp[i - 1] + cost[i - 1], dp[i - 2] + cost[i - 2]);
	}
	cout << dp[n];
 
	return 0;
}